Spark plug



Sept. 17, 1940. T. TOGNOLA SPARK PLUG Filed June 25, 1938 INVENTOR. TULLIO TOGNOLA f BY %%a 4 A TTORNEY Patented Sept. 17, 1940 UNITED STATES PATENT OFFICE SPARK PLUG poration of Delaware Application June 25, 1938, Serial No. 215,712

' 7 Claims. (01. 123-169) This invention relates to ignition systems for internal combustion engines and more particularly to spark plugs.

One object of the invention is to provide an improved spark plug which embodies novel means for preventing the escape of gases from the engine cylinder through the spark plug structure with a consequent loss of compression.

Another object of the invention is to provide a spark plug embodying a novel gas-tight seal and an improved shielding means which on account of its simplicity and small number of parts is rugged in structure, cheap to manufacture and easy to assemble.

Still another object of the invention is to provide a spark plug with improved heat dissipation from the nose electrode.

A further object of the present invention is to provide an improved spark plug which is both 0- mechanically and electrically strong, and is :capable of long service without mechanical or electrical faults.

A still further object of the invention is to provide a spark plug embodying improved insulat- 25 ing properties without reducing the heat dissipating properties.

These and other objects will appear more fully in the detailed description of the invention which follows. Although only one embodiment of the ;0 present invention is illustrated in the accompanying drawing, it is to be expressly understood that this drawing is for the purpose of illustration only and is not to be construed as a limitation of the scope of the invention, reference being had {5 primarily for this purpose to the appended claims. In the accompanying drawing forming part hereof:

Fig. '1 is a longitudinal sectional view of one embodiment of the invention. 0 Fig. '2 is a sectional view taken on line 2--2 of Fig-1.

Fig. 3 is a bottom plan view showing one embodiment of grounded electrode design.

Referring first to Fig. 1, reference character I 5 designates a metallic extension of the cylinder engaging base or shell 2, there being an intermediate polygonal portion 3 which receives the wrench or other tool for insertion of the plug in the cylinder wall. The lower portion of element 3 I is also shown as provided with a polygonal section 4 facilitating its attachment to shell 2, but

it is to be understood that the two members I and 2 may be integral if preferred. The extension I may be provided with cooling fins such as I0. 5 The central electrode comprises a spindle 5 having at its lower end an enlarged head 6 which serves as the sparking point. A copper heat conducting sleeve I surrounds spindle 5 throughout' its entire length resting at its lower end on head 6. An insulator 8, preferably a mica cigarette surrounds copper sleeve 1 practically throughout'its entire length. A stack of insulating washers 9, preferably of mica, surrounds the lower portion of electrode 5, copper sleeve I and insulating cigarette 8 abutting head 5, pref- 1o erably being of increasing outer diameter away from said head. The upper end of the stack of insulating washers 9 abuts against the lower end of core nut 4.

Lining the lower enlarged bore or core nut 4 is 5 an insulating sleeve I2, preferably a mica cigarette. Abutting mica insulating washers 9 and shoulder II of core nut 4 respectively are stacks of mica insulating washers I3 and I4 and located between said stacks of washers, concentric with mica cigarettes 8 and I2 is a metallic ring I5 having the qualities of good heat conductivity and a relatively large coefficient of expansion, such as aluminum. The purpose of insert ring I5 will be more fully explained hereinafter.

Spindle 5 with copper sleeve I and mica cigarette 8 project through and are also in intimate contact with a decreased bore of core nut 4.

Lining the upper enlarged bore of core nut I which constitutes the shield extension I is an an insulating sleeve I6 preferably a mica cigarette. The upper end of shield extension I is spun over so as to assist in positioning mica cigarette I6 and to guard it against fraying when an ignition cable is inserted in the spark plug.

Surrounding insulating sleeve 8 of electrode 5 in the upper enlarged bore of core nut 4 is a stack of insulating washers II, preferably of mica, bearing at one end on core nut 4 and held tightly in place by the washer I8 which in-turn is held by the flared out portion I9 of central electrode 5.

In the assembly of the spark plug the portion I 9 is flared out by hydraulic means so that all of the insulating discs are tightly held together thereby assisting in the prevention of gas leakage.

Attached to shell 2 is a grounded cap electrode 2I which may be fastened to it in any well known manner. In the preferred method of fastening, electrode 2I is formed with annular groove such as 22 and a portion of shell 2 is staked in so 5 as to give it a mechanical look as can be seen at 23 in Figs. 1 and 2. As an additional fastening means electrode 21 may be silver soldered, brazed or welded to the shell 2.

The shell 2 is inwardly threaded as at 24 so as 5 to receive the thread portion 25 of core nut 4 and having therebetween a washer 26, preferably made of copper.

Metallic insert ring 15 has at least a two fold purpose in that it affords a better path for the conduction of heat and due to its expansion it afiords a sealing means to prevent gas leakage. The heat path of the plug ordinarily without insert I5 would be along the copper heat conducting tube 3 and spindle 5 to mica washers such as l3 and M to 25 and 24 and thence to the engine block and to the cooling fins I0. An alternate path is also had through the portion ll of the core nut *2. With the use of metal insert E5 the non-metallic heat path is shortened since the heat does not have to traverse the mica discs and it can be conducted through metal insert 15.

Of prime importance is the fact that the expansion of the metal insert l5 presents an additional gas sealing means for the spark plug. The lengthwise expansion of insert l5 causes the stack of mica washers M to be forced against core nut i, the stack 9 being forced against the head 6 of electrode 5, and the force is transmitted through the spindle of electrode 5 to the stack ll. It is therefore apparent that the mica washers are held very tightly together, creating a gas-tight fit. The expansion of insert l5 also presses the mica cigarette against the inner walls of the lower end of core nut 4.

Various changes, which will now appear to those skilled in the art, may be made in the form, details of construction and arrangement of the parts without departing from the spirit of the invention, and reference is to be primarily had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In a spark plug, a body portion, insulating means lining the walls of said body portion, an insulated electrode therein, said insulated electrode being surrounded by a stack of insulating discs, a metallic ring having a high coefficient of expansion mounted between the insulated walls of said body and the insulated central electrode and between said insulating discs whereby heat expansion of said metallic ring compresses the insulating lining, the insulation surrounding the central electrode and the stack of insulating discs.

2. In a spark plug, a body member, a mica lining for said body member, a central electrode within said body and a mica cigarette surrounding said central electrode, a stack of mica discs surrounding said central electrode, an expansible metallic insert positioned between said mica cigarette and the lining of said body member and between said mica discs whereby expansion of said metallic insert compresses the mica insulation.

3. In a spark plug, a hollow shell member having an internal shoulder therein, an electrode extending through said shoulder, insulating means lining the walls of said shell member, an insulating sleeve surrounding the electrode, a stack of insulating discs surrounding the electrode above said shoulder, another stack of insulating discs directly beneath said shoulder, a third stack of insulating discs surrounding the electrode near its lower extremity, a metallic expansible insert disposed concentric with the electrode between the second and third mentioned stacks of insulating discs.

4. In a spark plug having an insulated central spindle surrounded partly by a stack of insulating discs, and an insulation lined enclosing shell, the combination with said discs, insulated spindle and lined shell of metallic means having a relatively high thermal coefficient of expansion, such as aluminum concentric with said spindle and said lined shell and positioned within said stack of insulating discs for compressing said insulation to prevent leakage of gas.

5. A spark plug comprising a tubular body, a

center electrode in said body, electrical insulating 5 material interposed between said body and said electrode, and a metallic element surrounding said electrode and embedded in said insulating material, said element being electrically insulated by said material from both said body and said electrode.

6. A spark plug comprising a tubular body, insulating means lining at least a portion of the inner wall of said body, a center electrode in said body, an insulating sleeve surrounding said electrode, and radially expandible metallic means having a relatively high thermal coeflicient of expansion interposed between said insulating lining means and said sleeve.

7.'A spark plug comprising a tubular body, said body having an enlarged bore at one end thereof forming an internal shoulder therein, a center electrode in said body, an insulating sleeve surrounding said electrode, an insulating sleeve lining the enlarged bore of said body, a metallic ring in said enlarged bore between said insulating sleeves, and stacks of insulating discs in said bore at opposite ends of said ring.

TULLIO TOGNOLA. 

